Sodium-rich layered oxide positive electrode material and preparation method and application thereof

Abstract

The invention provides a sodium-rich layered oxide positive electrode material and a preparation method and application thereof, and belongs to the technical field of sodium ion batteries, the sodium-rich layered oxide is of a P2 structure, the space group is P63 / mmc, and the chemical general formula is NaxNiaFebMncAdO2, wherein 0.9 < = x < = 1.1, 0.1 < = a, 0.1 < = b, 0.5 < = c, and 0 < = d < = 0.3; a is selected from one or more of Li, K, Mg, Al, Ca, Ti, V, Cr, Co, Cu, Zn, Zr, Nb, Mo, Sn, Ta, W, Sb and La. The main elements of the sodium-rich layered oxide are Na and Mn, and the addition amount of Na is limited to be greater than or equal to 0.9, so that the charging specific capacity of the P2-type positive electrode material is remarkably improved, the traditional cognition that the P2-type layered oxide positive electrode material is difficult to industrially apply due to sodium deficiency is broken, and a new view angle is provided for promoting the industrial application of the P2-type positive electrode material.

Description

Technical Field

[0001] The present invention belongs to the technical field of sodium ion batteries, and in particular relates to a sodium-rich layered oxide positive electrode material and a preparation method and application thereof. Background Art

[0002] At present, lithium-ion batteries, as the main representative of electrochemical energy storage, can greatly improve the utilization efficiency of renewable energy. However, with the rapid development of electric vehicles around the world, the demand for power batteries is growing. In addition, the global lithium resource reserves are limited, expensive and unevenly distributed, making it difficult to meet the needs of power vehicles and large-scale energy storage at the same time. Sodium-ion batteries, with their advantages of abundant resources, wide distribution, low cost and high safety, can serve as a beneficial supplement to lithium-ion batteries and emerge in the field of large-scale energy storage.

[0003] Positive electrode materials for sodium ion batteries include oxides, polyanions, Prussian blue and organic materials. Among them, layered oxides have high theoretical specific capacity, moderate working voltage, high compaction density, low toxicity and are easy to prepare on a large scale, which has attracted widespread attention from the scientific research community and the industry. Layered oxides are divided into P2 type and O3 type. In P2 type layered oxides, sodium ions migrate directly from one octahedral position to another octahedral position, while O3 type layered oxides need to pass through adjacent tetrahedral positions and need to overcome a larger migration energy barrier. Therefore, the rate performance of P2 type materials is generally better than that of O3 type materials. However, the commercial application of P2 type materials still faces challenges. P2 type materials have a very low charge capacity due to severe sodium deficiency. With carbon materials as the negative electrode, the capacity is limited in the full battery system, which is a major bottleneck hindering its commercial application. Summary of the invention

[0004] Based on the above background issues, the present invention aims to provide a sodium-rich layered oxide positive electrode material and its preparation method and application, so that the charge capacity of the P2 type positive electrode material can be significantly improved, breaking the traditional perception that the P2 type layered oxide positive electrode material is difficult to industrialize due to the lack of sodium.

[0005] The technical solution adopted by the present invention to achieve the above-mentioned purpose is:

[0006] The present invention provides a sodium-rich layered oxide, wherein the sodium-rich layered oxide has a P2 structure, a space group of P63 / mmc, and a chemical formula of: Na x Ni a Fe b Mn c A d O 2 ;

[0007] Among them, 0.9≤x≤1.1, 0.1≤a, 0.1≤b, 0.5≤c, 0≤d≤0.3;

[0008] A is one or more of Li, K, Mg, Al, Ca, Ti, V, Cr, Co, Cu, Zn, Zr, Nb, Mo, Sn, Ta, W, Sb and La.

[0009] The present invention also provides a method for preparing the above-mentioned sodium-rich layered oxide, comprising: preparing a precursor containing the required metal element, heat treating it at 400-600°C for 3-6h, and then heat treating it at 700-1100°C for 5-24h to obtain the sodium-rich layered oxide.

[0010] Preferably, the precursor is prepared by the following method: sodium carbonate and oxygen-containing compounds of other metals Ni, Fe, Mn, and A are uniformly mixed according to a stoichiometric ratio to obtain a precursor powder.

[0011] More preferably, the oxygen-containing compound is one or more of oxides, hydroxides, carbonates and acetates.

[0012] More preferably, the D50 of the precursor powder is 0.03-10 um, preferably 0.5-2 um.

[0013] Preferably, the precursor is prepared by the following method:

[0014] a. dissolving the desired metal salt in water according to a stoichiometric ratio, stirring and dissolving to obtain a mixed salt solution;

[0015] b. adding a chelating agent to the mixed salt solution, and then stirring and evaporating the mixed salt solution at 60-120°C to obtain a precursor gel; or

[0016] The mixed salt solution is spray-dried to obtain a precursor powder.

[0017] More preferably, the chelating agent is at least one of citric acid, oxalic acid, polyethylene glycol, chitosan, glucose, polyvinyl alcohol, and ethylenediaminetetraacetic acid.

[0018] More preferably, the inlet temperature of the spray drying is 200-300°C, and the outlet temperature is 80-120°C.

[0019] Preferably, the precursor is prepared by the following method: dissolving metal salts of other metals Ni, Fe, Mn, and A in water according to a stoichiometric ratio to obtain a salt solution; mixing the salt solution with a sodium hydroxide solution and an ammonia solution to generate a precipitate, aging, washing, drying, and sieving the precipitate to obtain a precursor powder of other metals; and uniformly mixing the precursor powder of other metals with sodium carbonate according to a stoichiometric ratio.

[0020] More preferably, the total salt concentration in the salt solution is 1-3 mol / L, the concentrations of the sodium hydroxide solution and the ammonia solution are both 1-3 mol / L, and the pH value of the mixture of the salt solution, the sodium hydroxide solution and the ammonia solution is 9-12.

[0021] More preferably, the volume ratio of the salt solution to the sodium hydroxide solution and the ammonia solution is 1:(2-3):(1-2).

[0022] The present invention further provides the use of the sodium-rich layered oxide in a sodium ion secondary battery.

[0023] The beneficial effects of the present invention are:

[0024] The main elements of the sodium-rich layered oxide provided by the present invention are Na and Mn, and the addition amount of Na is limited to be greater than or equal to 0.9, so that the charge capacity of the P2 type positive electrode material is significantly improved, breaking the traditional perception that P2 type layered oxide positive electrode materials are difficult to industrialize due to lack of sodium, and providing a new perspective for promoting the industrial application of P2 type positive electrode materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The XRD spectrum of the sodium-rich layered oxide positive electrode material of the present invention;

[0026] Figure 2 The XRD spectrum of the sodium-rich layered oxide positive electrode material in Example 1 of the present invention;

[0027] Figure 3 This is a graph showing the first charge and discharge test results of a battery formed of a sodium-rich layered oxide positive electrode material in Example 1 of the present invention in a voltage range of 2-4.2V;

[0028] Figure 4 This is a graph showing the test results of the cycle performance of a battery formed of the sodium-rich layered oxide positive electrode material in Example 1 of the present invention in the voltage range of 2-4.2V;

[0029] Figure 5 This is the XRD spectrum of the sodium-rich layered oxide positive electrode material in Example 5 of the present invention;

[0030] Figure 6 This is a graph showing the first charge and discharge test results of a battery formed of a sodium-rich layered oxide positive electrode material in Example 5 of the present invention in a voltage range of 2-4.2V;

[0031] Figure 7 This is a graph showing the test results of the cycle performance of a battery formed of a sodium-rich layered oxide positive electrode material in Example 5 of the present invention in the voltage range of 2-4.2V;

[0032] Figure 8 This is the XRD spectrum of the sodium-rich layered oxide positive electrode material in Example 6 of the present invention;

[0033] Fig. 9 This is a graph showing the first charge and discharge test results of a battery formed of a sodium-rich layered oxide positive electrode material in Example 6 of the present invention in a voltage range of 2-4.2V;

[0034] Fig.10 This is a graph showing the test results of the cycle performance of a battery formed of a sodium-rich layered oxide positive electrode material in Example 6 of the present invention in the voltage range of 2-4.2V;

[0035] Fig.11 This is the XRD spectrum of the sodium-rich layered oxide positive electrode material in Example 7 of the present invention;

[0036] Fig.12 This is a graph showing the first charge and discharge test results of a battery formed of a sodium-rich layered oxide positive electrode material in Example 7 of the present invention in a voltage range of 2-4.2V;

[0037] Fig.13 This is a graph showing the cycle performance test results of a battery formed of the sodium-rich layered oxide positive electrode material in Example 7 of the present invention in the voltage range of 2-4.2V. DETAILED DESCRIPTION

[0038] In order to explain the present invention more clearly, the present invention is further described in detail below in conjunction with embodiments and with reference to the accompanying drawings. It should be understood by those skilled in the art that the content described below is illustrative rather than restrictive, and should not be used to limit the scope of protection of the present invention.

[0039] The present invention provides a sodium-rich layered oxide, wherein the sodium-rich layered oxide has a P2 structure, a space group of P63 / mmc, and a chemical formula of: Na x Ni a Fe b Mn c A d O 2 , XRD spectrum as Figure 1 As shown;

[0040] Among them, 0.9≤x≤1.1, 0.1≤a, 0.1≤b, 0.5≤c, 0≤d≤0.3;

[0041] A is one or more of Li, K, Mg, Al, Ca, Ti, V, Cr, Co, Cu, Zn, Zr, Nb, Mo, Sn, Ta, W, Sb and La.

[0042] Example 1

[0043] The sodium-rich layered oxide has a P2 structure, a space group of P63 / mmc, and a chemical formula of Na 0.95 Ni 0.1 Fe 0.15 Mn 0.7 Sn 0.05 O 2 , XRD spectrum as Figure 2 As shown, it was prepared by the following method:

[0044] (1) according to the stoichiometric ratio, sodium carbonate, nickel oxide, ferric oxide, manganese dioxide and tin dioxide are mixed uniformly by a high-speed mixer to obtain a precursor powder with a D50 of 1 μm;

[0045] (2) In an oxygen atmosphere, the precursor powder is heat treated at 500° C. for 5 h and then at 850° C. for 15 h to obtain a sodium-rich layered oxide.

[0046] Example 2

[0047] The sodium-rich layered oxide has a P2 structure, a space group of P63 / mmc, and a chemical formula of Na 0.95 Ni 0.1 Fe 0.15 Mn 0.7 Sn 0.05 O 2 , prepared by the following method:

[0048] (1) dissolving sodium carbonate, nickel acetate, ferric nitrate, manganese acetate and tin tetrachloride in water according to a stoichiometric ratio, and stirring to obtain a mixed salt solution;

[0049] (2) adding citric acid to the mixed salt solution, and then stirring and evaporating the mixed salt solution at 80° C. to obtain a precursor gel;

[0050] (3) The precursor gel is heat treated at 500° C. for 4 h and then at 800° C. for 15 h to obtain a sodium-rich layered oxide.

[0051] Example 3

[0052] The sodium-rich layered oxide has a P2 structure, a space group of P63 / mmc, and a chemical formula of Na 0.95 Ni 0.1 Fe 0.15 Mn 0.7 Sn 0.05 O 2 , prepared by the following method:

[0053] (1) dissolving sodium carbonate, nickel acetate, ferric nitrate, manganese acetate and tin tetrachloride in water according to a stoichiometric ratio, and stirring to obtain a mixed salt solution;

[0054] (2) spray drying the mixed salt solution at an inlet temperature of 250° C. and an outlet temperature of 100° C. to obtain a precursor powder;

[0055] (3) The precursor powder is heat treated at 600° C. for 3 h and then at 900° C. for 12 h to obtain a sodium-rich layered oxide.

[0056] Example 4

[0057] The sodium-rich layered oxide has a P2 structure, a space group of P63 / mmc, and a chemical formula of Na 0.95 Ni 0.1 Fe 0.15 Mn 0.7 Sn 0.05 O 2 , prepared by the following method:

[0058] (1) dissolving nickel acetate, ferric nitrate, manganese acetate and tin tetrachloride in water according to a stoichiometric ratio to obtain a salt solution, wherein the total salt concentration in the salt solution is 2 mol / L;

[0059] (2) mixing the salt solution with a sodium hydroxide solution and an ammonia solution in a volume ratio of 1:2.5:1.5 to generate a precipitate, wherein the concentrations of the sodium hydroxide solution and the ammonia solution are both 2 mol / L, and the pH of the mixture of the salt solution, the sodium hydroxide solution and the ammonia solution is 10, and aging, washing, drying and sieving the precipitate to obtain a precursor powder;

[0060] (3) The precursor powder and sodium carbonate are uniformly mixed according to a stoichiometric ratio, heat treated at 500° C. for 5 h, and then heat treated at 950° C. for 10 h to obtain a sodium-rich layered oxide.

[0061] Example 5

[0062] The sodium-rich layered oxide has a P2 structure and a space group of P63 / mmc. The XRD pattern is as follows Figure 5 As shown, the difference from Example 1 is that the chemical formula of the sodium-rich layered oxide is: Na 0.9 Ni 0.15 Fe 0.15 Mn 0.7 O 2 The preparation method of this embodiment is the same as that of embodiment 1.

[0063] Example 6

[0064] The sodium-rich layered oxide has a P2 structure and a space group of P63 / mmc. The XRD pattern is as follows Figure 8 As shown, the difference from Example 1 is that the chemical formula of the sodium-rich layered oxide is: Na1.0 Ni 0.1 Fe 0.1 Mn 0.7 Li 0.05 Ti 0.05 O 2 The preparation method of this embodiment is the same as that of embodiment 1.

[0065] Example 7

[0066] The sodium-rich layered oxide has a P2 structure and a space group of P63 / mmc. The XRD pattern is as follows Fig.11 As shown, the difference from Example 1 is that the chemical formula of the sodium-rich layered oxide is: Na 1.1 Ni 0.15 Fe 0.1 Mn 0.68 Sn 0.02 Mg 0.05 O 2 The preparation method of this embodiment is the same as that of embodiment 1.

[0067] Example 8

[0068] The sodium-rich layered oxide has a P2 structure and a space group of P63 / mmc. Different from Example 1, the chemical formula of the sodium-rich layered oxide is: Na 0.9 Ni 0.1 Fe 0.15 Mn 0.7 Ti 0.05 O 2 The preparation method of this embodiment is the same as that of embodiment 1.

[0069] Example 9

[0070] The sodium-rich layered oxide has a P2 structure and a space group of P63 / mmc. Different from Example 1, the chemical formula of the sodium-rich layered oxide is: Na 0.95 Ni 0.1 Fe 0.15 Mn 0.7 Mg 0.02 Cu 0.03 O 2 The preparation method of this embodiment is the same as that of embodiment 1.

[0071] Example 10

[0072] The sodium-rich layered oxide has a P2 structure and a space group of P63 / mmc. Different from Example 1, the chemical formula of the sodium-rich layered oxide is: Na 1.0 Ni 0.1 Fe 0.1 Mn 0.7 Sn 0.03 Li0.5 Mg 0.06 Ti 0.06 O 2 The preparation method of this embodiment is the same as that of embodiment 1.

[0073] Embodiment 11

[0074] The sodium-rich layered oxide has a P2 structure and a space group of P63 / mmc. Different from Example 1, the chemical formula of the sodium-rich layered oxide is: Na 0.95 Ni 0.1 Fe 0.1 Mn 0.5 Sn 0.3 O 2 The preparation method of this embodiment is the same as that of embodiment 1.

[0075] Example 12

[0076] The sodium-rich layered oxide has a P2 structure and a space group of P63 / mmc. Different from Example 1, the chemical formula of the sodium-rich layered oxide is: Na 0.95 Ni 0.1 Fe 0.1 Mn 0.6 Sn 0.2 O 2 The preparation method of this embodiment is the same as that of embodiment 1.

[0077] Test example

[0078] 1. Preparation of sodium ion batteries

[0079] The application of sodium-rich layered oxide positive electrode material in sodium ion secondary battery, specifically using the sodium-rich layered oxide positive electrode material as the positive electrode material of the sodium ion secondary battery, the assembly of the sodium ion secondary battery includes the following steps:

[0080] (1) mixing sodium-rich layered oxide positive electrode material powder with conductive agent SP and binder PVDF in a mass ratio of 8:1:1, adding solvent N-methyl methyl pyrrolidone (NMP), and stirring uniformly in a room temperature dry environment to form a slurry;

[0081] (2) The slurry in step (1) was evenly coated on the current collector aluminum foil, dried in an oven at 80°C for 12 h, cut into pole pieces with a diameter of 13 mm, dried at 120°C for 4 h under vacuum conditions, and then transferred to an Ar atmosphere glove box for standby use;

[0082] (3) Assemble CR2032 button cells in an argon glove box, using metallic sodium as the negative electrode and NaPF 6 / (EC:DMC:PC)

[0083] solution as electrolyte.

[0084] 2. Electrochemical performance test

[0085] Use constant current charge and discharge mode to perform charge and discharge tests in the 2-4.2V voltage range.

[0086] like Figure 3 and 4 As shown, it can be seen that the battery formed by the sodium-rich layered oxide positive electrode material in Example 1 of the present invention has a discharge specific capacity of 127.68 mAh / g at a current density of 0.1C, a first coulombic efficiency of 88.64%, a discharge specific capacity of 110.4 mAh / g at a current density of 1C, a discharge specific capacity of 102.12 mAh / g after 100 cycles at a rate of 1C, and a capacity retention rate of 92.5%.

[0087] like Figure 6 and 7 As shown, it can be seen that the battery formed by the sodium-rich layered oxide positive electrode material in Example 5 of the present invention has a discharge specific capacity of 141.64 mAh / g at a current density of 0.1C, an initial coulombic efficiency of 89.82%, a discharge specific capacity of 112.47 mAh / g at a current density of 1C, and a discharge specific capacity of 96.17 mAh / g after 100 cycles at a rate of 1C, with a capacity retention rate of 85.51%.

[0088] like Fig. 9 and 10 As shown, it can be seen that the battery formed by the sodium-rich layered oxide positive electrode material in Example 6 of the present invention has a discharge specific capacity of 153.26 mAh / g at a current density of 0.1C, an initial coulombic efficiency of 91.52%, a discharge specific capacity of 121.5 mAh / g at a current density of 1C, a discharge specific capacity of 102.46 mAh / g after 100 cycles at a rate of 1C, and a capacity retention rate of 84.33%.

[0089] like Fig.12 and 13 As shown, it can be seen that the battery formed by the sodium-rich layered oxide positive electrode material in Example 7 of the present invention has a discharge specific capacity of 116.73 mAh / g at a current density of 0.1C, an initial coulombic efficiency of 93.54%, a discharge specific capacity of 100.52 mAh / g at a current density of 1C, a discharge specific capacity of 87.18 mAh / g after 100 cycles at a rate of 1C, and a capacity retention rate of 86.73%.

[0090] Table 1. Electrochemical performance test results of Examples 1, 5, 6, and 7

[0091]

[0092] The charge capacity of the sodium-rich layered oxide positive electrode material in the embodiment of the present invention is significantly improved, breaking the traditional perception that P2-type layered oxide positive electrode materials are difficult to industrialize due to sodium deficiency, and providing a new perspective for promoting the industrialization of P2-type positive electrode materials.

[0093] Obviously, the above embodiments of the present invention are merely examples for more clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made on the basis of the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the protection scope of the present invention.

Claims

1. Sodium-rich layered oxide, the sodium-rich layered oxide has a P2 structure, a space group of P63 / mmc, and a chemical formula of: Na x Ni a Fe b Mn c A d O 2 ; in, 0.9≤x≤1.1, 0.1≤a, 0.1≤b, 0.5≤c, 0≤d≤0.3; A is one or more of Li, K, Mg, Al, Ca, Ti, V, Cr, Co, Cu, Zn, Zr, Nb, Mo, Sn, Ta, W, Sb and La.

2. The method for preparing the sodium-rich layered oxide according to claim 1, include: A precursor containing the required metal element is prepared, heat treated at 400-600°C for 3-6 hours, and then heat treated at 700-1100°C for 5-24 hours to obtain a sodium-rich layered oxide.

3. The preparation method according to claim 2, It is characterized in that The precursor is prepared by the following method: sodium carbonate and oxygen-containing compounds of other metals Ni, Fe, Mn, and A are uniformly mixed according to a stoichiometric ratio to obtain a precursor powder.

4. The preparation method according to claim 3, It is characterized in that The oxygen-containing compound is one or more of oxides, hydroxides, carbonates and acetates.

5. The preparation method according to claim 2, It is characterized in that The precursor is prepared by the following method: a. dissolving the desired metal salt in water according to a stoichiometric ratio, stirring and dissolving to obtain a mixed salt solution; b. adding a chelating agent to the mixed salt solution, and then stirring and evaporating the mixed salt solution at 60-120°C to obtain a precursor gel; or The mixed salt solution is spray-dried to obtain a precursor powder.

6. The preparation method according to claim 5, It is characterized in that The chelating agent is at least one of citric acid, oxalic acid, polyethylene glycol, chitosan, glucose, polyvinyl alcohol and ethylenediaminetetraacetic acid; the inlet temperature of the spray drying is 200-300°C, and the outlet temperature is 80-120°C.

7. The preparation method according to claim 2, It is characterized in that The precursor is prepared by the following method: dissolving metal salts of other metals Ni, Fe, Mn, and A in water according to a stoichiometric ratio to obtain a salt solution; mixing the salt solution with a sodium hydroxide solution and an ammonia solution to generate a precipitate, aging, washing, drying, and sieving the precipitate to obtain a precursor powder of other metals; and uniformly mixing the precursor powder of other metals with sodium carbonate according to a stoichiometric ratio.

8. The preparation method according to claim 7, It is characterized in that The total salt concentration in the salt solution is 1-3 mol / L, the concentrations of the sodium hydroxide solution and the ammonia solution are both 1-3 mol / L, and the pH value of the mixed solution of the salt solution, the sodium hydroxide solution and the ammonia solution is 9-12.

9. The preparation method according to claim 8, It is characterized in that The volume ratio of the salt solution to the sodium hydroxide solution and the ammonia solution is 1:(2-3):(1-2).

10. Use of the sodium-rich layered oxide according to claim 1 in sodium ion secondary batteries.

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